Mesut Ozil has found himself under pressure to perform at this summer's World Cup after drawing criticism from fans and former players alike.

The Arsenal midfielder was booed by German supporters last Saturday as he was substituted following a disappointing performance in his country's 2-2 draw with Cameroon.

Joining fans in voicing his concern over Ozil's current offerings is former Germany captain Michael Ballack.

"It's difficult to say where his head is going to be at the World Cup," said Ballack. "I saw him play for the national team at the weekend and I was not surprised, not scared, but a little bit concerned, by his performances.

"He has done well for Germany, and he played well during the qualifying campaign, but in the last few months, since his move to Arsenal, he has not been the same player, in terms of his confidence that we used to see in the national team."

Germany coach Joachim Loew has also challenged Ozil, who moved to Arsenal in a £42.5 million deal last summer, to improve his on-pitch body language and show a greater strength of character.

That is a sentiment shared by Arsenal fans who were left angry with the German's attitude on several occasions last season, notably in the 6-3 defeat by Manchester City when he trudged off the field without acknowledging the support of the travelling fans.

"He is not a leader on the pitch, like a captain," he said. "People expect so much of him, but he can improve his body language massively because he is now at an age where he is no longer a young talent or a promising player.

"As one of our best players he has to take more responsibility, and we expect more from him at the moment. Hopefully, when the World Cup starts, we will see a different player."

Borussia Dortmund midfielder Marco Reus has been touted as a possible replacement for Ozil should Loew drop him for Germany's opening Group G game against Portugal.

But despite calls for him to be included in the starting XI at Ozil's expense, Reus insisted he is just happy to be a part of the World Cup squad.

"I have played the World Cup qualifiers on the left wing, and that position suits me fine," he said. "The Bundestrainer [Joachim Loew] also knows that I can play in the middle, on the right wing and in attack. I don't care which position I play - my goal is to play at the World Cup."